A storage system is known which reports a write end to a host computer when receiving a write request from the host computer and storing write data accompanying the write request in a cache memory area (hereinafter, a cache area). In addition, a storage system is also known which multiplexes (generally, duplexes) write data stored in a cache area to improve protection of the write data with respect to failures such as a power loss.
According to PTL1, when duplexing write data from the host computer, data protection is realized without sacrificing performance by eliminating exclusive control among a plurality of controllers having cache areas.
According to PTL2, in a storage system which stores user data by adding redundant data such as a parity to the user data, by storing updated data (write data) from the host computer in a different cache area from data prior to the update (old data), access to a storage apparatus during generation of the redundant data is reduced and processing efficiency of the storage system is improved.